keihn 39mm pwk on a 400ex

[hotrodbelair]

i got this carb from a friend of mine came off a snowmobile im wondering if id be able to run it on my ex? the only reason im asking cause someone said it wont work cause its made for 2 stroke.

[deathman53]

2 stroke carb on a 4 stroke, I don't think its gonna work. most 4 stroke carbs have accelerator pumps and are desighned better for the 4 stroke engine. with the acccelarator pump your 400ex starts a whole lot easier, I can tell you that.

[hotrodbelair]

if i had that carb on my ex all dialed in think it would get more power out of it then the stock carb? for engine mods i have 440 wesico 11:1, hotcam stroker cam, ported head, 3 angle valve job, 1mm bigger valves, fmf powerbomb header with hmf slip on. if that helps any.

[86 Quad R]

the carb will work on there but as stated will be hard to start at times. as for performance it will most definately wake the engine up. we had a 34mm on a modded warrior awhile back and the difference was daylight and dark.

[hotrodbelair]

yea when i first threw the carb on there to see how it fit. she didnt want to start but i never changed the jets yet. im gonna try it with the biggest jets i got wich is a 175 main 45 pilot, just to see if can keep it running for a while so i know where im at as far as jetting

[deathman53]

175 main???????, increase the pilot and decrease the main. lrd 310pv doesn't even use a 175. you also are gonna want to play with the needle to reduce and lacking/gurgering in the mid range

[hotrodbelair]

its raining pretty bad right now so ill fool around with it tonight and keep this thread up to date on what happens.

[hotrodbelair]

i put the 152 main in it and ran it for a little bit got a dry black plug. but when i was running it i was pumping the throttle a little bit then i let off to let it idle wich it did for a little bit then it started reving up so i shut it off. what would make that happen.

[hotrodbelair]

got her goin yesterday didnt get it spot on but close enough cause we ran out of jets. things a hell of a lot better then stock. and it started fairly easy. the jets were running in it is 145 main and a 42 pilot.

[Aceman]

I can't believe you even got that carb to work!! Good job. Let us know how it runs.:)

[1fst400]

Im no genius but I would say when you use a carb with no accelerator pump, you wont acclerate fast.


the acclerator pump gives the motor a little bit of gas when you jab the throttle. It squirts it in beore the engine can create enough vacuume to suck gas in the normal way.

with out one you get to much air, not enough gas.

Im shure it will run fine. But times when you want to get it up in a wheelie or somthing and you give it that quick jab, It will fall on its face. I know thats what my fcr carb does, it has a accel pump, but they're known for not being the best till you buy the 80$ upgrade.

[hotrodbelair]

that was the one problem i had if i gave it a quick jab to full throttle it would bog out. but thats only if im at idle then to full throttle but if im cruising around at around 1/4 throttle then go to full throttle it dont bog at all.